This is a collaborative work with the group of Prof. A. Yethiraj at Memorial University of Newfoundland, St. John's (Canada). Actually, the experiments presented here have been done in his laboratory, although we are now doing experiments with our spin-coater. The spin-coating technique applied to the colloidal crystallization [P. Jiang et al.J. Am. Chem. Soc. 126 (2004) 13778] [A. Mihi et al. Adv. Mater. 18 (2006) 2244] [C. Arcos et al. Phys. Rev. E 77 (2008) 050402(R)] has been thought to have two steps. Firstly, the colloid is spun in order to form a (relatively thin) layer on the substrate. Secondly, the spinning colloid structure is frozen by means of rapidly evaporating the solvent or by other techniques. In the research presented here, we prove that the dried structure (orientationally correlated polycrystal) is not the frozen colloid structure that existed in the spinning fluid. Our experimental way of proceeding is similar to previous experiments [C. Arcos et al. Phys. Rev. E 77 (2008) 050402(R)]

We studied the dynamics of drying during the process of spin-coating, where we focus on the transitions between symmetries in the fluid phase (6-fold symmetry to 4-fold symmetry to no evident symmetry to (through drying) 6 or 4-fold symmetry in outer part and 4-fold symmetry in the inner part) and their correlation with thinning rate of the fluid and with the movement of the drying front.

Our main contribution was in the experimental part (M. Giuliani) and in the analysis / discussion of data (W. González-Viñas).

We obtained (among other interesting things [M. Giuliani et al. J. Phys. Chem. Lett. 1 (2010) 1481]) that there appear new symmetry structural transitions in the fluid phase during spinning related to shear melting / ordering. Also, we found a suitable scaling for the thinning rate, which gives a collapse of all data to one universal curve, for which we were able to obtain a model. Also, we proved that the dynamics of the drying front is closely related to the final dried structure.

• • M. Giuliani et al. J. Phys. Chem. Lett. 1 (2010) 1481.

  • M. Giuliani, Ph.D. thesis. Universidad de Navarra (2010)

We acknowledge Professor Claude Daley for a loan of his high-speed camera. This work was partly supported by the Natural Science and Engineering Research Council of Canada, and by the Spanish MEC (ref. FIS2008-01126) and by Departamento de Educación (Gobierno de Navarra). M. Giuliani acknowledges partial financial support from the "Asociación de Amigos de la Universidad de Navarra".

Two different experimental configurations allow us to characterize the symmetry transitions dynamics (A), and the thinning rate (B):

Video (fast camera) for the symmetry transitions:

Video (fast camera) for the thinning rate measurements (through Newton rings interference pattern):